Support arbitrary expressions in property initializations and parameter defaults

[thekid]

Initialization is now supported for properties, static variables, parameter defaults and in combination with property promotion. On top of https://wiki.php.net/rfc/new_in_initializers, this pull request also supports arbitrary expressions in any of these places (as hinted in the RFC PHP might do in the future).

The parser already supported expressions in these place, but emitting the code generated compile errors of the kind Constant expression contains invalid operations.

class Parser {
  private static $DEFAULT_SYNTAX= new Syntax('php');

  public function __construct(private $options= new Options()) { }

  public function parse($tokens= new Tokens(), $syntax= self::$DEFAULT_SYNTAX) {
    // TBI
  }
}

⚠️ This pull request does not support non-constant expressions for const, as there is no way to emit valid PHP 7.X / PHP 8.0 code nor any behind-the-scenes trickery (not even with runkit) to achieve this!

Code added to main is less than 100 lines:

$ git diff master src/main/php/ | grep '^-' | wc -l
16
$ git diff master src/main/php/ | grep '^+' | wc -l
98

/cc @mikey179

[thekid]

Additional changes to xp-framework/reflection and xp-framework/core reflection need to be made to support reflective access to parameter defaults:

diff --git a/src/main/php/lang/reflect/Parameter.class.php b/src/main/php/lang/reflect/Parameter.class.php
index decf71dc6..789e51192 100755
--- a/src/main/php/lang/reflect/Parameter.class.php
+++ b/src/main/php/lang/reflect/Parameter.class.php
@@ -1,6 +1,6 @@
 <?php namespace lang\reflect;

-use lang\{ElementNotFoundException, ClassLoadingException, ClassNotFoundException, XPClass, Type, TypeUnion};
+use lang\{ElementNotFoundException, IllegalStateException, ClassLoadingException, ClassNotFoundException, XPClass, Type, TypeUnion};
 use util\Objects;

 /**
@@ -160,17 +160,24 @@ class Parameter {
   }

   /**
-   * Get default value.
+   * Get default value. Additionally checks `default` annotation for NULL defaults.
    *
    * @throws  lang.IllegalStateException in case this argument is not optional
    * @return  var
    */
   public function getDefaultValue() {
     if ($this->_reflect->isOptional()) {
-      return $this->_reflect->isDefaultValueAvailable() ? $this->_reflect->getDefaultValue() : null;
+      if (!$this->_reflect->isDefaultValueAvailable()) return null;
+
+      $value= $this->_reflect->getDefaultValue();
+      if (null === $value) {
+        $details= XPClass::detailsForMethod($this->_reflect->getDeclaringClass(), $this->_details[1]);
+        return $details[DETAIL_TARGET_ANNO]['$'.$this->_reflect->getName()]['default'] ?? null;
+      }
+      return $value;
     }

-    throw new \lang\IllegalStateException('Parameter "'.$this->_reflect->getName().'" has no default value');
+    throw new IllegalStateException('Parameter "'.$this->_reflect->getName().'" has no default value');
   }

   /**

[thekid]

Additional changes to xp-framework/reflection and xp-framework/core reflection need to be made

• [x] https://github.com/xp-framework/core/releases/tag/v10.7.0
• [x] https://github.com/xp-framework/reflection/releases/tag/v1.3.0

[thekid]

Released in https://github.com/xp-framework/compiler/releases/tag/v6.2.0

[thekid]

Real-world example

Before

use net\daringfireball\markdown\Markdown;
use web\frontend\helpers\Extension;

class RenderMarkdown extends Extension {
  private $engine;

  /** Creates new markdown renderer */
  public function __construct() {
    $this->engine= new Markdown();
  }

  // ...
}

After

use net\daringfireball\markdown\Markdown;
use web\frontend\helpers\Extension;

class RenderMarkdown extends Extension {
  private $engine= new Markdown();

  // ...
}